U.S. Pat. No. 3,408,229 granted on Oct. 29, 1968 discloses an electric cell having a negative electrode based on an alkali or alkali-earth metal, e.g. based on lithium in solution in ammonia, a positive electrode comprising a solution of thiocyanates and sulphur in ammonia, and a thin, cellophane-based membrane separating said positive electrode from said negative electrode.
However, the work done by the Applicant has made it evident that the teachings contained in said U.S. patent do not make it possible to provide an electric cell which operates adequately.
Firstly, the Applicant has observed that membranes based on cellophane are not stable in the proposed medium (e.g. Li(NH.sub.3).sub.4) and are very rapidly destroyed.
Secondly, thiocyanates are not stable in the presence of the sulphur positive electrode, and decompose to give cyanides.
Thirdly and above all, since the cathode solution contains sulphur and wets the separator, it diffuses therethrough and mixes with the anode mass, thereby short-circuiting the cell. This is due to the fact that contrary to what is set forth by the authors of said patent, cellophane does not, in actual fact, constitute an effective barrier against sulphur dissolved in an ammonia solution nor against lithium in an ammonia solution.
Preferred embodiments of the present invention remedy these drawbacks.